We present here a review of the most significant recent achievements in the field of HAXPES (HArd X-ray PhotoElectron Spectroscopy) on isolated atoms and molecules, and related spectroscopies. The possibility of conducting hard x-ray photoexcitation and photoionization experiments under state-of-the art conditions in terms of photon and electron kinetic energy resolution has become available only in the last few years. HAXPES has then produced structural and dynamical information at the level of detail already reached in the VUV and soft-x-ray ranges. The much improved experimental conditions have allowed extending to the hard x-ray range some methods well established in soft x-ray spectroscopies. Investigations of electron and nuclear dynamics in the femtosecond (fs, 10-15 sec) and even attosecond (as, 10-18 sec) regime have become feasible. Complex relaxation phenomena following deep-core ionization can now be enlightened in great detail. Other phenomena like e.g. recoil-induced effects are much more important in fast photoelectron emission, which can be induced by hard x-rays. Furthermore, a new kind of ionic states with double core holes can be observed by x-ray single-photon absorption. Future perspectives are also discussed.

中文翻译：

---

孤立原子和分子的硬 X 射线光谱和动力学：综述

我们在此回顾了 HAXPES（硬 X 射线光电子能谱）领域对孤立原子和分子以及相关光谱学的最新成就。在光子和电子动能分辨率方面，在最先进的条件下进行硬 X 射线光激发和光电离实验的可能性仅在最近几年才变得可用。HAXPES 然后在 VUV 和软 X 射线范围内已经达到的细节水平上产生结构和动力学信息。大大改进的实验条件允许将一些在软 X 射线光谱中已经很好建立的方法扩展到硬 X 射线范围。飞秒（fs，10-15 秒）甚至阿秒（10-18 秒）范围内的电子和核动力学研究已变得可行。现在可以非常详细地揭示深核电离后的复杂弛豫现象。其他现象如反冲诱导效应在快速光电子发射中更为重要，这可以由硬 X 射线诱导。此外，通过X射线单光子吸收可以观察到一种具有双核孔的新型离子态。还讨论了未来的前景。